The Posterior Cruciate Ligament (PCL) is found within your knee, just behind the Anterior Cruciate Ligament (ACL). It is one of the ligaments that holds the femur to the tibia, keeping the tibia from moving backwards in relation to the thigh bone. While a strong ligament, the PCL can be injured after being subjected to a powerful force — common causes include a knee joint hitting a dashboard in a car accident, or an athlete falling on a bent knee. Depending on your symptoms and the severity of your pain, you might be referred for an MRI scan to confirm the injury and determine the best course of treatment.
An MRI scanner uses radio waves and a large magnetic field to take images of your body's hard and soft tissues. To assess your PCL injury and its severity, your doctor will take an MRI scan of your affected leg. This is a non-invasive procedure that gives your healthcare professional a clear picture of your injury without the need for more invasive measures.
MRIs are an excellent option for leg injuries as they can show the surrounding area and identify any additional injuries alongside the PCL, giving your doctor a thorough understanding of what treatment you need.
MRI imaging is considered the gold standard for the evaluation of PCL injury, with an accuracy of between 96% and 100%. It is one of the quickest and most effective ways of confirming a PCL injury, which is why most healthcare professionals recommend it when dealing with PCL injury symptoms. If you are experiencing any of the following, your doctor might refer you for an MRI: pain in the knee and leg that worsens over time; swelling; a feeling of instability in the knee; stiffness; difficulty walking; or trouble walking down stairs.
MRIs can also assess the other ligaments and tendons around your knee to check for additional injuries, and can quickly determine which grade your PCL injury is — there are four grades, each requiring a different level of treatment.
Most MRI scans of the knee are straightforward and don't require significant preparation, although you may be given a list of requirements before attending. PCL injuries can be very painful and some patients may be fast-tracked into their scan, leaving little time to prepare.
If you do have time, there are generally no restrictions on eating or drinking, though some hospitals prefer you to restrict food for a certain number of hours beforehand — your doctor will advise.
As the MRI machine is a large magnet, remove all metal before your appointment. Leave jewellery and other metal items at home, and inform your doctor of any metal medical devices such as pacemakers or pins from previous injuries. If these cannot be removed, it is possible you may not be able to have the scan due to safety concerns.
On the day of your scan, radiology staff will walk you through what to expect. Once you are comfortable and your questions have been answered, you will be given clothes to change into and a designated space for your belongings. Remove everything other than the provided clothing — including earrings, hearing aids, and any remaining metal items.
Most PCL MRI scans do not require a contrast medium, so the radiologist will take you straight into the scan room and position you on the bed. Headphones and a choice of music will be provided, as the machine can be quite loud. If you are feeling anxious, ask about a light sedative before the scan begins.
The scan typically takes between 30 and 60 minutes, as the technician will likely take images across all three planes (axial, coronal, and sagittal). You can speak to your radiologist at any time throughout the scan.
After the scan, you will be taken to your locker to change and collect your belongings. If your procedure was outpatient, you should be able to go home straight away. Depending on the severity of your injury, you may be asked to wait for same-day results. If a sedative was given, you may need to wait for it to wear off. Otherwise, your doctor should be in contact within a few days to discuss findings and next steps.
Relatively non-invasive
Compared to other exploratory options such as X-rays and surgery, an MRI of the knee is far less invasive.
Shows several areas of the knee at once
PCL injuries can affect more than just the ligament itself, so being able to view the full surrounding area helps your doctor create the most effective treatment plan.
Clearest form of imagery
Compared to other imaging technologies such as X-rays, MRIs offer significantly clearer images, providing a better insight into your injuries.
May fast-track your recovery
The sooner your PCL injury is assessed, the sooner a personalised treatment plan or surgery can be arranged, getting you on the road to recovery as quickly as possible.
There are very few risks associated with PCL MRI scans, as they do not use ionising radiation. They are relatively non-invasive and quick, though it is vital to disclose all medical devices to your doctor beforehand — including pins, splints, piercings, and body modifications from past surgeries or procedures.
Although rare, some PCL MRIs may require a contrast medium to get a clearer image of the internal structures of the knee. Allergic reactions to this have been reported in rare cases, so disclose any known allergies to your doctor ahead of the scan.
Your doctor might order a PCL MRI if you are showing symptoms of a sustained injury following a traumatic incident to your bent knee joint. An ultrasound or X-ray may be used first, but if these do not reveal a clear injury, an MRI scan is likely to follow.
Most PCL MRI scans take between 30 and 60 minutes, though some may take up to 90 minutes if images are unclear or if movement occurred during the scan.